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  1. #1

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    GPR won't start then huge backfire!

    I have done a lot of reading here but cant find anything specific. My motor won't start on its own, I then put some gas and oil down each cylinder and crank it. Doesn’t start but I get a huge boom that even blew off the exhaust after the stinger! It sounds like a cannon going off and tons of smoke. So loud that the neighbors even came out!

    Here is what I know.
    - Before I put the exhaust on I was getting this issue and would have a small fire in the exhaust manifold.
    - There was a lot of oil in the crankcase from putting in a new crank. Could this cause an issue?
    - Bottom end was from another ski so its not the same flywheel, would that cause some type of timing issue?
    - Compression is great
    - I installed the carbs after installing the motor into the hull, would an air leak between the motor and carbs cause this? may have torn the gasket and not noticed it.??

    I have rebuilt many of these motors and have never had an issues like this. Any help would be appreciated! Just at a loss at this time and need a place to start.


  2. #2
    Happily Self-Employed WFO's Avatar
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    big band means its not firing correctly... what flywheel is on it? keyway sheared? crank out of phase?

  3. #3

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    Its all oem. I bought the bottom end put together but they guy did have to put new seals in it. Flywheel is stock as well. How do I check the crankshaft phasing?

  4. #4
    Happily Self-Employed WFO's Avatar
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    1200 or 1300 flywheel? they are not the same

    one to TDC, the others should be equal length from the top

  5. #5

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    Thanks, sure enough I contacted the guy that sold it to me and he did put a different flywheel on there by mistake. Installed my old one and good to go! Thanks for your help! Just need a waterbox now since the explosion blew mine to pieces!

  6. #6
    Mike xsockguyx's Avatar
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    Quote Originally Posted by richte18 View Post
    Thanks, sure enough I contacted the guy that sold it to me and he did put a different flywheel on there by mistake. Installed my old one and good to go! Thanks for your help! Just need a waterbox now since the explosion blew mine to pieces!
    1200 or 1300? I got a 1300 waterbox for sale. $60

  7. #7
    Moderator RX951's Avatar
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    Exclamation

    make sure you check those reeds for cracks since you had a backfire. backfires are not good on the reeds.

  8. #8
    Cajundude's Avatar
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    Sounds like a broken flywheel, right Rich?

  9. #9
    Happily Self-Employed WFO's Avatar
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    Quote Originally Posted by Cajundude View Post
    Sounds like a broken flywheel, right Rich?

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